1. Field of the Invention
The present invention relates to a sliding-type magnetic head for magnetooptically recording information on a magnetooptical recording medium in sliding contact therewith.
2. Description of the Relevant Art
One of optical disks for storing, erasing, and retrieving information with a light beam is known as a magnetooptical disk.
As shown in FIG. 1 of the accompanying drawings, a conventional magnetooptical disk 1 comprises a transparent substrate 2, a magnetooptical recording layer 3 in the form of a perpendicularly magnetizable film disposed on the transparent substrate 2 with an SiN protective film 8 interposed therebetween, a reflecting film 4 in the form of a thin metal film such as an aluminum film disposed on the magnetooptical recording layer 3 with another SiN protective film 8 interposed therebetween, and a protective film 5 as of an ultraviolet-curing resin disposed on the reflecting film 4.
Field- and beam-modulating recording processes are known for recording information on magnetooptical disks.
The field-modulating recording process is capable of recording information in an overwrite mode in which a new signal is recorded over an old signal on the magnetooptical disk. The field-modulating recording process will be described below with reference to FIG. 2 of the accompanying drawings. An optical pickup for applying a laser beam 6 is disposed on one side of a magnetooptical disk 1 with a magnetooptical recording layer in the form of a perpendicularly magnetizable film, i.e., on the substrate side of the magnetooptical disk 1, and a magnetic field generator, i.e., a magnetic head 7, is disposed on the other side of the magnetooptical disk 1, i.e., on the protective film side, for movement in synchronism with the laser spot. The direction of the magnetic field generated by the magnetic head 7 is varied by varying the direction of an electric current supplied to the magnetic head 7.
In operation, the magnetooptical disk 1 is rotated about its own center at a predetermined speed.
It is assumed that a magnetic field representing a recording signal is generated in the vicinity of a laser spot 6a on the magnetooptical disk 1. A region 1A of the magnetooptical disk 1, in which recorded information is to be rewritten, is heated to the Curie temperature by the laser spot 6a and hence demagnetized. When the region 1A is moved out of the laser spot 6a on rotation of the magnetooptical disk 1, the temperature of the region 1A drops below the Curie temperature, and the region 1A is magnetized in the direction of the applied magnetic field, thus recording the signal.
The magnetooptical disk 1 is a non-contact recording medium, i.e., the magnetic head 7 is spaced from the magnetooptical disk 1 by a predetermined distance d.sub.0.
The applicant has developed an ultrasmall-size digital recording and reproducing apparatus for digitally recording information on and reproducing information from a small-size magnetooptical disk.
Since the conventional magnetic head 7 is held out of contact with a magnetooptical disk 1 when recording information thereon, the magnetic head 7 is associated with an electromagnetic servomechanism for causing the magnetic head 7 to follow disk surface displacements that occur due to any inclination of the magnetooptical disk 1, thickness irregularities thereof, etc., when the magnetooptical disk 1 rotates. The presence of the electromagnetic servomechanism has posed limitations on a recording and reproducing apparatus with respect to efforts to reduce power consumption and apparatus size (particularly apparatus thickness).
If a magnetic head is held in sliding contact with a magnetooptical disk, then the magnetic head can be supported by a simple support structure, dispensing with an electromagnetic servomechanism which takes up a large space. Therefore, a recording and reproducing apparatus with a magnetic head designed to held in sliding contact with a magnetooptical disk may be reduced in power requirements and size.
The magnetooptical disk 1 has surface irregularities such as bumps or the like. When a magnetic head held in sliding contact with the magnetooptical disk 1 passes a bump, the magnetic head jumps away from the disk surface by a distance corresponding to the height of the bump, resulting in a reduction in recording capability. To maintain a desired level of recording capability, the magnetic head is required to have a higher power output.
Shocks that are applied to the magnetooptical disk by the sliding-type magnetic head are proportional in magnitude to the weight of the magnetic head. When such shocks are imposed on the magnetooptical disk, the magnetooptical disk vibrates, causing an optical system coupled to the magnetic head to be defocused. In order to reduce shocks applied to the magnetooptical disk, the magnetic head should be reduced in weight and hence size. However, inasmuch as smaller-size magnetic heads produce lower output levels, they fail to meet the requirement for higher power output.